Plant Process and Function

en Optimizing Peppermint (Mentha piperita L.) essential oil yield and quality: Roles ‎of nitrogen, salicylic acid, and weed management Optimizing Peppermint (Mentha piperita L.) essential oil yield and quality: Roles ‎of nitrogen, salicylic acid, and weed management تنظیم کننده های رشد گیاهی Plant Growth Regulators پژوهشي Research <div style="text-align: left;">Peppermint has anti-inflammatory, antiseptic, and soothing properties due to its essential oil content. This plant is widely used in the pharmaceutical, cosmetic, and food industries and helps relieve stomachaches, headaches, and stress. The primary objective of this study was to evaluate the combined effects of nitrogen (N), salicylic acid (SA), and weed management on morphophysiological traits, essential oil content, and essential oil yield of peppermint. The present study was conducted under field conditions at Sari, Mazandaran Province, northern Iran, during the 2023–2024 growing season. In this research, a factorial arrangement within a randomized complete block design (RCBD) with three replications was conducted, which included three nitrogen (N) levels (0, 1.5, and 3 g L-¹), three salicylic acid (SA) levels (0, 1.5, and 3 mM), and two weed management practices (weeding vs. non-weeding). Results indicated that the increase in N and SA significantly enhanced plant height, chlorophyll content, biological yield, and essential oil content. Notably, the treatment with 3 g/L of N and 3 mM of SA without weed control showed the best results in increasing essential oil yield (169 kg ha⁻¹) and essential oil content (2.65%). This treatment also improved the absorption of nutrients such as N, phosphorus (P), and potassium (K), while increasing the plant's resistance to environmental stresses. These findings suggest that optimal management of N and SA, even under mild weed stress, can significantly enhance both the quality and quantity of peppermint yields. Therefore, this research can serve as a valuable reference for farmers and researchers aiming for sustainable production of this medicinal plant with reduced synthetic inputs.</div> Peppermint has anti-inflammatory, antiseptic, and soothing properties due to its essential oil content. This plant is widely used in the pharmaceutical, cosmetic, and food industries and helps relieve stomachaches, headaches, and stress. The primary objective of this study was to evaluate the combined effects of nitrogen (N), salicylic acid (SA), and weed management on morphophysiological traits, essential oil content, and essential oil yield of peppermint. The present study was conducted under field conditions at Sari, Mazandaran Province, northern Iran, during the 2023–2024 growing season. In this research, a factorial arrangement within a randomized complete block design (RCBD) with three replications was conducted, which included three nitrogen (N) levels (0, 1.5, and 3 g L-¹), three salicylic acid (SA) levels (0, 1.5, and 3 mM), and two weed management practices (weeding vs. non-weeding). Results indicated that the increase in N and SA significantly enhanced plant height, chlorophyll content, biological yield, and essential oil content. Notably, the treatment with 3 g/L of N and 3 mM of SA without weed control showed the best results in increasing essential oil yield (169 kg ha⁻¹) and essential oil content (2.65%). This treatment also improved the absorption of nutrients such as N, phosphorus (P), and potassium (K), while increasing the plant's resistance to environmental stresses. These findings suggest that optimal management of N and SA, even under mild weed stress, can significantly enhance both the quality and quantity of peppermint yields. Therefore, this research can serve as a valuable reference for farmers and researchers aiming for sustainable production of this medicinal plant with reduced synthetic inputs. Essential oil, Nitrogen, Peppermint, Salicylic acid, Weed management Essential oil, Nitrogen, Peppermint, Salicylic acid, Weed management 65 76 http://jispp.iut.ac.ir/browse.php?a_code=A-10-1968-1&slc_lang=en&sid=1 Hossein Mazloomi Hossein Mazloomi No Department of Agronomy, Faculty of Crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari 4818168984, Iran. Department of Agronomy, Faculty of Crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari 4818168984, Iran. Rahmat Abbasi Rahmat Abbasi Yes Department of Agronomy, Faculty of Crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari 4818168984, Iran. Department of Agronomy, Faculty of Crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari 4818168984, Iran. Arastoo Abbasian Arastoo Abbasian No Department of Agronomy, Faculty of Crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari 4818168984, Iran. Department of Agronomy, Faculty of Crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari 4818168984, Iran. Hematollah Pirdashti Hematollah Pirdashti No Department of Agronomy, Faculty of Crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari 4818168984, Iran. Department of Agronomy, Faculty of Crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari 4818168984, Iran. Seyed Mostafa Emadi Seyed Mostafa Emadi No Department of Soil Science, Faculty of Crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari 4818168984, Iran. Department of Soil Science, Faculty of Crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari 4818168984, Iran.